The present invention relates to a method to improve a gas phase reactor polymerization process by injecting a cooled recycle gas directly into the plenum of a gas phase reactor, preferably during high levels of a condensing mode gas phase process.
Advances in polymerization and catalysis have resulted in the capability to produce many new polymers having improved physical and chemical properties useful in a wide variety of superior products and applications. With the development of new catalysts, the choice of polymerization conditions (solution, slurry, high pressure or gas phase) for producing a particular polymer has been greatly expanded. Also, advances in polymerization technology have provided more efficient, highly productive and economically enhanced processes. Especially illustrative of these advances is the development of technology utilizing bulky ligand metallocene catalyst systems in slurry or gas phase. There is a desire in the industry using this technology to reduce the complexity of the process, to improve the process operability, to increase product characteristics and to vary catalyst choices. Thus, it would be advantageous to have a process that is capable of improving one or more of these industry needs.
In particular there exists a need in the industry to improve gas phase reactor operations and operation costs and/or resin particle formation in gas phase systems that can polymerize olefins using a solution fed catalyst system.
The temperature of the plenum gas flow in a gas or slurry phase system affects the performance of the catalyst. If the temperature is too low, such as for example near or below the dew point of the cycle gas, the catalyst system injected into the region of the fluidized bed at the plenum takes longer to dry and in the presence of rapid polymerization systems may lead to the formation of small resin particle agglomerates of deficient size and morphology for optimal fluid bed operation. If the temperature of the plenum gas flow is too high, the spray or slurry containing the catalyst system may dry out too rapidly resulting in extremely fine resin particles or particles fusing together due to high temperatures and poor cooling during the initial stages of polymerization. Catalyst productivity may also be reduced by excessive initial temperatures of the plenum gas flow. It is desirable to control temperature of the plenum gas flow (particle deflecting gas) within a range that, depending upon the particular catalyst and process conditions, results in high catalyst activity and a resin morphology conducive to good mixing and operation of the fluid bed reactor.
U.S. Pat. No. 5,693,727 discloses plenum usage in gas phase polymerization where the recycle stream or a portion thereof is cooled and the recycle stream is returned directly to the reactor.
The instant invention provides a method to control plenum gas flow temperature by cooling a portion of the recycle gas and returning it to one reactor via the plenum.
This invention relates to a method to polymerize olefin(s) comprising contacting one or more monomer(s) with a catalyst system in a gas phase reactor having a recycle system, for removing a recycle gas and unreacted monomer(s) from the reactor and returning the recycle gas and fresh monomer(s) to the reactor, and a plenum, the method comprising the steps of: (a) cooling the recycle gas to form a cooled recycle gas; (b) optionally combining the cooled recycle gas with additional recycle gas; and (c) injecting the cooled recycle gas into the gas phase reactor through the plenum.